Yes, similar to bitcoin. When a mining pool is close to having 51% of the hashrate, the community and the miners themselves call on some of them to mine in another mining pool.
Also, a similar situation can happen today without Asics.
By chance, sometimes I saw coins which had dominant hashrates (more than 60% or even higher) concentrated on one pool.
Of course, it's rarely scenario when all hashrates of the pool controlled by one address/ group / farm, but it is always a very bad signal of potential serious Replay Attacks.
This can also occur in GPU mined cryptocoins, however. 51% attacks are not exclusive incidents for Asic mined coins. Low hashrate coins are also easier to attack, that was why Aeon staying with the Asics
might have been better.
Also, replay attacks? I reckon you do not know what it means. Replay attacks only occur when there is a fork in the blockchain, where transactions in the original chain can be
replayed in the forked chain.